I agree, longer is better, especially if you have progressive coils. I contacted several vendors, and most agreed that to protect the front driveshaft, you front shocks should be no longer than 650mm. The 5160's have a short compressed length that you can extend them an inch or so without running into issues with overcompressing them, providing you are running bump stops for your tyres. You can always go with the longer ones, and use limiting straps to limit their travel as well, once again, the compressed length is comparitively short so you need minimal bump stop for the shocks.